Method for clearing coating material from perforated pipe



July 20, 1965 H. R. RALSTON METHOD FOR CLEARING COATING MATERIAL FROM PERFORATED PIPE Filed March 31. 1961 INVENTOR. HARRY i2. RALsTo BY ATTQRNEVS.

United States Patent Office 3,1963% Patented July 20, 1965 3,196,042 METHGD FOR CLEARING CGATHNG MATERLAL F'RQM PERFURATED PIPE Harry R. Ralston, West Middletown, Ohio, assignor to Armco Steel tjorporation, Middletown, Ohio, a corporation of Dhio Filed Mar. 31, 1961, Ser. No. 99,891 3 Claims. (Cl. 11794) This invention relates to perforated pipe and the clean ing of coating materials, such as asphalt, from the perforations in such pipe.

In the manufacture of perforated pipe, such as corrugated metal pipe utilized for subsurfaces drainage, it is the general practice to dip coat the pipe sections in asphalt or other similar coating material to enhance the corrosion resistance of the pipe. In accordance with prior art practices, the pipe sections were simply immersed in a bath of molten asphalt and then removed and allowed to cool, whereupon the holes or perforations in the pipe sections, which were closed by a skin of asphalt, were cleared by use of a hand punch which was dipped in oil between successive strokes to prevent asphalt pick up. As can be appreciated, the clearing of the perforations in the manner just described is a time consuming operation and adds materially to the cost of fabricating the pipe sections.

A principal object of the instant invention is the provision of procedures by means of which the perforations in coated drain pipe may be rapidly and efficiently cleared with the complete elimination of the hand punching operation heretofore employed for the purpose.

A further object of the instant invention is the provision of a perforation clearing technique in which the ends of a pipe section to be cleared are first sealed, whereupon a partial vacuum is created within the pipe section, the greater pressure of the outside air being utilized to force open the skin of asphalt covering the perforations and thereby clear them of obstructions.

The foregoing, together with other objects of the instant invention which will appear hereinafter or which will be apparent to the skilled Worker in the art upon reading this specification, I accomplish by that construction and arrangement of parts of which I shall now describe an exemplary embodiment.

Reference is now made to the accompanying drawings wherein:

FIGURE 1 is a side elevational view of an aspirator device in accordance with the instant invention illustrating the manner in which it is associated with the end of a pipe section to be cleared.

FIGURE 2 is a vertical sectional view taken along the line 22 of FIGURE 1.

FIGURE 3 is a vertical sectional view taken along the line 33 of FIGURE 1.

FIGURE 4 is an enlarged vertical sectional view taken along the line 44 of FIGURE 1.

FiGURE 5 is an elevational view on reduced scale illustrating the manner in which the pipe being cleared is tilted during the clearing operation.

Referring first to FIGURE 1, I have therein illustrated a pipe section 1 provided with a plurality of spaced apart perforations 2 which, in conventional drainage pipe, are usually confined to one side only of the pipe section, thereby permitting drainage water and the like to enter the pipe and be carried from the field. From the outset is should be understood that the size and configuration of the pipe sections do not constitute a limitation upon the invention, although in most instances the invention will be applied to corrugated pipe having diameters ranging from 6 to 21 inches. Similarly, the size and number of perforations do not constitute a limitation upon the in vention, it being contemplated that the instant invention will be applicable to the clearing of diverse classes of perforated pipe sections.

Asphalt is the most common coating medium for pipe sections of the character under consideration, it being customary to submerge the pipe sections in a tank of molten asphalt, whereupon the sections are removed and drained of excess asphalt. It has been found, however, that for the instant procedure to be effective, the clearing operation must be conducted within a period of several minutes after removal of the pipe from the dip tank. While the time will vary somewhat depending upon the type of asphalt employed and its temperature, it would appear that the optimum time to apply the vacuum to the inside of the pipe is about 1 /4 minutes after removal of the pipe from the dip tank, with a leeway of from V2 minute to 3 minutes after removal of the pipe from the asphalt tank. Preferably, the asphalt on the pipe will be at a temperature of from about 300 to 350 F. for ideal clearing, although it has been found that these temperatures may vary 1 70 F. depending upon the exact nature of the asphalt employed. In terms of viscosity, a viscosity of about seconds (Saybolt-Furol) has been found highly desiraable; and in this connection it may be noted that the temperature at which an asphalt has a given viscosity will vary somewhat with the composition of the asphalt. However, it may be additionally observed that the asphalt should be sufficiently viscous so that it will not string out from the perforations or plug up the aspirator; and yet it must be soft enough to unplug easily.

The usable vacuum range will vary with the viscosity of the asphalt at the time of clearing. It is preferred, however, to employ a vacuum of about 1-6 inches of Water at the aspirator end of the pipe section, which results in corresponding values of 0.54 inches of water at the opposite end of the pipe section. Care must be taken, however, to prevent the asphalt from being drawn into the aspirator.

With the foregoing considerations in mind, reference is again made to FIGURE 1 of the drawings wherein it will be seen that the pipe section to be cleared is closed at one end by a plug member 3 which may conveniently comprise a flat plate 4 of imperforate character provided with a handle 5. It will be understood that upon the removal of a coated pipe section from the dip tank, the face 6 of the plug member be juxtaposed to one end of the pipe section so as to make essentially sealing contact therewith. No special precaution need be taken for this purpose since the asphalt coating on the end edges of the pipe section will assist in effecting a tight closure; although if desired, the face 6 of the plug may be provided with a gasket or the like arranged to make contact with the annular end edge of the pipe section. In this connec tion, it may be pointed out that the pipe sections are normally suspended from an overhead crane or similar rig during dipping and draining. Usually a plurality of the pipe sections will be dipped simultaneously, whereupon the rig will be moved away from the dip tank for removal of the sections. In accordance with the instant invention, the dipped pipe sections may be readily moved to a clearing station where a team of two persons may rapidly clear the pipe sections, one member of the team handling the plug member 3 and the other the aspirator device now to be described.

With reference to FIGURES 1 and 2, the aspirator is provided with a head 7 comprising a face plate 8 adapted to make sealing contact with the opposite end of the pipe section, the face plate having a circular opening 9 therein which is of a smaller diameter than the diameter of the pipe section being cleared. The face plate is preferably provided with a plurality of guide pins 16 arranged to align the end of the pipe section relative to the opening 9. Extending rearwardly from the opening 9 is an aspirator tube 11, the tube 11 effectively opening into the end of the pipe section through the opening 9 in the face plate 8. Preferably, the head 7 is provided with a mounting plate 12 which serves to mount the aspirator tube 11 and at the same time provides a convenient mounting means for the conduit 13 which supplies air under pressure to the aspirafor tube. As will be evident from FIGURE 1, the conduit 13 is provided with a fitting 13a to which a flexible hose or the like may be connected to supply air under pressure, as from a source indicated at 14.

As will be evident from FIGURES 3 and 4, the conduit 13 is preferably arranged to surround a major portion at least of the aspirator tube 11 and it is provided with spaced apart connections 15, 16 and 17 connected to aspirator pipes 18, 19 and 20, respectively, which passed through the aspirator tube 11 and terminate in orifices 21, 22 and 23 extending rearwardly of the aspirator tube and directed parallel to the walls of the tube, the orifices preferably being spaced apart by 120. As will be evident, the aspirator pipes 18, 19 and 20 direct air jets rearwardly through the tube 11 and hence act to draw a partial vacuum at the open leading end at the tube 11 and in the pipe section to be cleared.

As will be evident from FIGURE 3, the opposite sides of the conduit 13 preferably extend outwardly beyond the opposite side edges of the mounting plate 12 (which is shown in dotted lines), and these portions effectively provide gripping handles by means of which the operator may grasp the aspirator unit and juxtapose the face plate 8 against the end edge of the pipe section. As will be apparent, valve means may be provided by means of which the operator may control the introduction of compressed air into the aspirator.

' In using the device, it is preferred that the end of the pipe section to which the aspirator is applied should be elevated slightly with respect to the opposite end to insure that any unsolidified asphalt Within the pipe does not run out of the bottom of the pipe and into the aspirator. The proper position of the aspirator and pipe is illustrated in FIGURE 5 of the drawings wherein it will be seen that the pipe is tilted from the horizontal, as indicated by the line A-A, with the end of the pipe closed by the plug member 3 lowermost. As already indicated, it is necessary for the clearing operation to be conducted within several minutes following the removal of the pipe section from the dip tank; and consequently there is a possibility that the asphalt will not have completely set.

Having, thus, described my invention in an exemplary embodiment, and with the understanding thatmodification may be made in it without departing from its spirit and purpose, what I desire to secure and protect by Letters Patent is:

1. A method of simultaneously clearing all of the per forations in a length of perforated pipe which has been dipped in a bath of molten asphalt and a skin formed over the perforations as an incident of the dipping operation, which comprises closing one end of the pipe by means of an essentially imperforate plug following removal of the pipe from the bath but at a time when the freshly applied coating is in a softened condition, and drawing a partial vacuum on the opposite end of thepipe, whereby to reduce the internal air pressure in the pipe and cause the external air to rupture the skin formed over the perforations in said pipe.

2. The method claimed in claim 1 wherein said partial vacuum is drawn on the coated pipe within a period of from /2 to 3 minutes from the time the pipe is removed from the bath, and wherein the partial vacuum drawn on the pipe is from 1 to 6 inches of water at the end of the pipe at which the vacuum is drawn.

3. The method claimed in claim 1 wherein the pipe is tilted slightly from the horizontal with the plugged end thereof lowermost.

CHARLES WILLMUTH, Examiner. 

1. A METHOD OF SIMULTANEOUSLY CLEARING ALL OF THE PERFORATIONS IN A LENGTH OF PERFORATED PIPE WHICH HAS BEEN DIPPED IN A BATH OF MOLTEN ASPHALT AND A SKIN FORMED OVER THE PERFORATIONS AS AN INCIDENT OF THE DIPPING OPERATION, WHICH COMPRISES CLOSING ONE END OF THE PIPE BY MEANS OF AN ESSENTIALLY IMPERFORATE PLUB FOLLOWING REMOVAL OF THE PIPE FROM THE BATH BUT AT A TIME WHEN THE FRESHLY APPLIED COATING IS IN A SOFTENED CONDITION, AND DRAWING A PARTIAL VACUUM ON THE OPPOSITE END OF THE PIPE, WHEREBY TO REDUCE THE INTERNAL AIR PRESSURE IN THE PIPE AND CAUSE THE EXTERNAL AIR TO RUPTURE THE SKIN FORMED OVER THE PERFORATIONS IN SAID PIPE. 